The disease known as "mono" is mononucleosis, which is caused by a virus called Epstein-Barr. It commonly affects teenagers, and it is characterized by a feeling of weakness and tiredness that may last for weeks or months.
The condition can be undetected in a person because its symptoms are usually mild, as stated by WebMD. Mono can be spread from one person to another through kissing, hence earning the name "kissing disease." It can also be spread through sharing items, such as toothbrushes and drinking glasses. The symptoms of the condition include fever, night sweats, headache, sore throat, muscle weakness, swollen tonsils and fatigue.